Material or article handling – Process – Of moving material between zones having different pressures...
Reexamination Certificate
2001-06-27
2002-12-17
Keenan, James W. (Department: 3652)
Material or article handling
Process
Of moving material between zones having different pressures...
C414S217000, C414S939000
Reexamination Certificate
active
06494670
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to loading and unloading of vacuum chambers while a vacuum is maintained in the chamber. More specifically, the invention relates to a load lock apparatus for loading silicon substrates in a substrate processing platform.
2. Background of the Related Art
Cluster tools which combine numerous substrate processing units in a processing platform have become generally accepted as an effective and efficient concept in advanced microelectronics manufacturing. A cluster tool generally refers to a modular, multi-chamber, integrated processing system. It typically consists of a central wafer handling vacuum chamber and a number of peripheral vacuum process chambers. The silicon wafers go through a set of process steps under vacuum in the various process stations without being exposed to ambient conditions. The transfer of the wafers for the processes is managed by the wafer handling vacuum chamber which is also maintained under vacuum conditions. Cluster tools offer significantly higher yields on account of lower defect densities. Different types of cluster tools, such as linear or radial, with different types of architecture are possible.
Substrate processing platforms typically include at least two load lock chambers mounted on separate openings in the central wafer handling vacuum chamber for loading or unloading silicon wafers while the vacuum chamber remains under vacuum. The load lock chambers occupy valuable positions on the processing platform which would otherwise be used for additional process chambers. However, two chambers are usually required to maintain continuous operation such that wafers are processed from one load lock chamber while finished wafers are unloaded from the other chamber and new wafers are loaded.
FIG. 1
(prior art) shows a commercially available substrate processing platform offered by Applied Materials, Inc. under the trademark Endura®. The platform combines vacuum chambers designed to process silicon wafers at low/high pressure vacuum in the range of 10
−3
to 10
−8
torr.
Referring to
FIG. 1
, silicon wafers in a cassette
10
are introduced and withdrawn from the platform
52
through a first slit valve by a first load lock chamber
12
or through a second slit valve by a second load lock chamber
14
. A first robot
16
having a blade
18
is located in a buffer chamber
20
to move a wafer
22
between various chambers
24
,
26
,
28
surrounding the buffer chamber
20
. A second robot
30
is located in a transfer chamber
32
to transfer a wafer
34
between various chambers
28
,
36
surrounding the transfer chamber
32
. The buffer chamber
20
and the transfer chamber
32
are connected through two common chambers
28
. It is understood in the art that a wafer may be processed or cooled in one or more chambers for any number of times in any order to accomplish fabrication of a desired semiconductor structure on the wafer. A microprocessor controller
38
and associated software is provided to control processing and movement of wafers.
Attempts to connect two or more load lock chambers to a single slit valve in a processing platform have been unsuccessful. Such an apparatus must have internal valves large enough for the transfer of entire cassettes of wafers. Large valves are difficult to seal when the load lock chamber is open to the atmosphere and is mounted on a chamber that is under high vacuum.
It is an objective of the present invention to provide a load lock apparatus for mounting two load lock chambers on a single slit valve in a substrate processing platform. It is a further objective of this invention to provide a large valve in a load lock chamber which will remain sealed when the load lock chamber is mounted on an opening in a vacuum chamber under high vacuum conditions.
SUMMARY OF THE INVENTION
The present invention provides a functional load lock apparatus having two or more load lock chambers mounted on a central chamber which can be mounted on a single opening in a vacuum chamber such as a substrate processing platform for making integrated circuits on silicon wafers.
The present invention also provides a load lock apparatus having a semi-cylindrical valve mounted in a load lock chamber. The semi-cylindrical valve remains sealed when the load lock chamber is open to atmospheric pressure. A wafer cassette holder positioned within each load lock chamber can be loaded and unloaded while the semi-cylindrical valves seal the vacuum chambers from atmospheric pressure. The semi-cylindrical valve pivots to an open position when the load lock chamber is under vacuum and the entire wafer cassette moves from the load lock chamber to the central chamber.
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Novellus Brochure.
Applied Materials Inc.
Keenan James W.
Moser, Patterson and Sheridan, LLP
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